When Ubisoft bought M&M rights I gave up on the series since there is almost no other good turn based game development team like old NWC. However, I totally forgot about Nival.
Both Etherlords and Silent Storm games were great tactical strategy game. Now that Nival picked up HoMM there is a chance for the series to not just keep going(which it has been doing since H2) but actually improve. Use your skills Nival and make this game as great as H2 was! It might be your ticket to both reviving the turn based strategy ganra and making Nival one of the best game development houses in the world.
Things I want to see in H5:
1) A passworded hotseat waiting screen so I don't have to watch my oponent all the time in case she is ready to use my turn
2)No heroes fighting in the battles! keep it like it was in H2 and Ehterlords. They can cast spells or add bonuses but they shouldn't be a moveble unit.
3)Better net support. A robust netcode and a matching service similar to Battle.net. You know that it might make or break this franchise, so please don't go the way of H4!
Simple and easy to use multiplayer will do more than any ammount of money wasted into voice actors!
4) Speaking of voice actors, don't use them!
The worst parts of Nival games were voiceovers.
If you don't have a great voice team like Blizzard does, DON'T do them at all.
It will save you money and won't ruin the game immersion. Nothing ruins the game more than a subpar voiceovers.
5)Support your fanbase. In gaming history fan support and dedication(fanboism?) has made even weak games sell well. Look at Diablo2 and WoW!
Those games are weak especially for Blizzard to make them, but a strong fansite community and dedication has made these games succesful and fun to play. Give regular updates to the fansites and keep the fans happy and you will have far more marketing done for you for free than any annoying popups on the net can do.
Don't add too much to the game, it should be easy and fun to play. It should be balanced and not too confusing. This way you can get to a far more diverse customer base than just
hardcore HoMM fans and other turn based fanatics.
7) Opera in town screens
8) Actually make some form of cat a unit,
I would say a diamond lion golem would be fine. Oh, and has to be stronger than the black dragons and Titans. You do have Titans and dragons planed right?